Nutrition 101: Carbohydrates

by Elle Penner, MyFitnessPal Registered Dietitian

Love ‘em or leave ‘em (personally, I’m a fan), carbohydrates are found in nearly everything – fruits and vegetables, grains, nuts and seeds, dairy, sweets, soda, the list goes on. Carbohydrates provide around half of the energy in a well-balanced diet, 45-65% of calories according to the most recent Dietary Guidelines for Americans, and similarly so in Australia and the UK.

Carbohydrate Metabolism

After eating a meal, carbohydrates are separated from dietary fiber and broken down into three monosaccharides (simple sugars): glucosefructose, and galactose. These monosaccharides are absorbed in the small intestine and enter the the blood stream. Much like a car that runs on unleaded fuel, our cells only take up carbohydrates in the form of glucose, so the liver first converts all of the fructose and galactose into glucose.

Glucose is transported through the blood stream and is:

  1. Immediately taken up by cells and turned into energy
  2. Stored as glycogen in the liver and skeletal muscles. Glycogen in muscles is turned back into glucose for energy during exercise and liver glycogen is what maintains our blood glucose levels during short fasting periods, like while we sleep.
  3. Converted into fatty acids and triglycerides for long-term energy storage, if consumed in excess

Types of Carbohydrates
They may all be broken down and turned into glucose, but all carbohydrates are not created equal. Some are more nutritionally dense than others; different types are digested at different rates and have different impacts on our blood sugar.


Complex carbohydrates are mostly found in whole grains, starchy vegetables, legumes, nuts, and seeds. They contain longer, more complex chains of sugars and also contain some fiber, protein and/or healthy fats, as well as essential vitamins and minerals. The presence of fiber, protein, and fat slows digestion and therefore absorption of those monosaccharides, resulting in a more gradual insulin response as well as increased satiety–both very good things.

Simple carbohydrates come from healthy foods like fruits, vegetables, and low-fat dairy, but also less nutritionally-dense foods like refined grains (white bread, white rice, and traditional pasta), processed snacks and crackers, sweets and sugar-sweetened beverages like sodas. These foods contain mostly mono- and disaccharides, one and two-molecule sugars that are very quickly digested and absorbed into the bloodstream — quite the opposite of complex carbs. While fruits, vegetables, and dairy offer good stuff like vitamins, minerals, antioxidants, phytochemicals, fiber and water, refined grains, sweets and sodas, on the other hand, lack all of these extra nutrients, which is why they should be limited in the diet.

When it comes to choosing carbohydrates to eat or drink, nutrient-dense sources are the way to go. These include complex carbs like 100% whole grain bread and pasta, brown rice, starchy vegetables (just leave the nutrient-rich skins on those potatoes), legumes, nuts, seeds, low-fat dairy and plenty of fruits and vegetables. To maximize nutrition density and satiety from carbohydrates, limit simple sugars from refined grains, processed snack foods, sweets, and sugar-sweetened beverages.

Carbs have undoubtedly gotten a bad wrap (couldn’t resist the misspelling) over recent years but whether you love them or not–they’re in everything–and we can certainly all benefit from choosing the most nutrient-dense kinds.

See our Carbohydrates Infographic (English only).
 

 


Last Updated: Dec 07, 2016 05:09PM PST

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